Bobby School had 540 pupils and Tom School had 30% less pupils. When an equal number of pupils joined each school, the ratio of the pupils in Tom School to that in Bobby School became 5 : 4. How many pupils were there in both schools in the end?

	Bobby School	Tom School	Difference
Before	540		162
Change	+ ?	+ ?
After	5 u	4 u	1 u

Since an equal number of pupils joined each school, the difference in the number of pupils at first and in the end between the 2 schools remains the same.  Make the difference between the number of pupils in Bobby School and Tom School at first and in the end the same. 

Difference between the number of pupils in both schools at first
= 30% x 540
= ³⁰₁₀₀ x 540
= 162

Difference between the number of pupils in both schools in the end
= 5 u - 4 u
= 1 u

1 u = 162

Total number of pupils in both schools in the end
= 5 u + 4 u
= 9 u
= 9 x 162
= 1458

Answer(s): 1458